The present invention relates to a device and system for delivering on command any ratio of blood to blood-additive solution of a blood/solution mixture during cardio vascular and cardiac perfusion procedures and more particularly to intermittently and/or continuously delivering on command any ratio of blood to cardioplegia solution of a blood/cardioplegia mixture during cardiac or "open heart" surgery.
Generally, cardioplegia is used in conjunction with hypothermia. This technique is commonly called cold cardioplegia. Based on the preference of the cardiac surgical team, a crystalloid chemical solution or some mixture of the solution and blood mixture is intermittently or continuously perfused to arrest the heart. For example, using cold cardioplegia, the heart is reperfused approximately every twenty minutes to keep the heart arrested.
Recently, open heart surgeons are utilizing a new technique called warm continuous blood cardioplegia. This technique does not use hypothermia, rather, it continually uses a cardioplegia mixture of warm (approximately 37 degrees centigrade) oxygenated blood and solution mixture throughout the cardiac surgery. See The Perfusionist's Perspective of Warm Continuous Blood Cardioplegia: A New Technique of Myocardial Protection, A. Karim Jabr, C.P., and Antony Panos, M.D., Proceeding of the American Academy of Cardiovascular Perfusion, Vol. 10, Aug. 1989. This technique appears to be safe and effective in prolonging high risk procedures, prolonging operative time, substantially eliminating the period of ischemia, limiting the period and injury of reperfusion, attaining exceptional myocardial preservation, and abolishing the detrimental effects of hypothermia.
Generically, these methods fall under the general category of myocardial protection techniques. Whether the blood cardioplegia is warm or cold blood, or intermittently and continuous, the blood and solution mixture is predetermined, typically in a 4 to 1 ratio, blood to solution. Presently, the ratio of blood to solution is pre-operatively fixed by the diameter of the tubing transferring the blood (typically 1/4 inch diameter tubing) and the solution (typically 1/16 or 1/8 inch diameter tubing). Thus, the ratio is fixed throughout the operation. This manner of delivering the blood and solution can cause certain complications during the operation. In addition, the fixed ratio may cause certain complications on a patient by patient basis, during the operation.
For instance, simultaneously using tubings of different diameter in the same pump head can unfortunately cause bunching of the tubing or inappropriate occlusion of both the 1/4-inch and the 1/16-inch line. Obviously, bunching of the tubing could lead to adverse consequences for the patient as a result of the time that it takes the perfusionist or physician to correct the problem. In addition, changing the bunched tubing during the operation increases the chance of line contamination or air getting into the system. Hence, a single tube is desirable.
Further, the typically used ratios of blood to solution, e.g. 4:1 and 2:1, that are pre-operatively fixed, may not necessarily be the optimal ratio for the patient, either when initially perfusing the heart or reperfusing the heart to keep it arrested during the operation. In addition, delivering a fixed ratio of blood/solution mixture with warm cardioplegia, the heart is continually perfused with solution that is mostly composed of water, causing tissue cells to swell. When the heart is revived, non-blood fluids in the tissue or lungs cause the heart to work harder, thereby straining the heart and prolonging recovery. Moreover, some heart surgery teams do not use a blood/solution mixture rather they perfuse the heart with pure solution. Whatever the preference may be, increasing the solution delivered to the heart using the present systems increases the total volume of fluid delivered to the heart and correspondingly varies the pressure on the aortic valve. Variation of the pressure on the aortic valve may affect the competency of the valve and may cause distension. Thus, it is desirable to control the amount of solution and/or vary the blood/solution ratio to customize the blood/solution mixture for each patient and to adjust this ratio during the operation or, if preferred, to intermittently deliver pure solution as necessary.
It would be highly advantageous therefore, to remedy the foregoing and other deficiencies and inherent limitations associated with the delivery of a blood/blood-additive solution mixture of a pre-determined ratio during cardio vascular and cardiac perfusion procedures.
Accordingly, it is a principal object of the device and system of the present invention to provide a device and system to selectively vary the ratio of blood to blood-additive solution from either all blood to pure solution and any ratio of the two, either continuously or intermittently, throughout the cardio vascular and cardiac perfusion procedure or surgery.
It is a object of the device and system of the present invention to provide a device and system that requires a single tube blood-additive solution pumping arrangement to deliver the blood and/or solution to the perfusion site.
It is a further object of the device and system of the present invention to vary the ratio of blood to solution without changing the total volume and maintaining a consistent pump flow rate and aortic pressure.
It is an advantage of device and system of the present invention to be utilized in either warm or cold cardioplegia.
It is a further advantage of the device and system of the present invention to permit the perfusionist to use either a single tube or double tube, blood-additive solution pumping arrangement.
It is a further advantage of the device and system of the present invention to permit the perfusionist to use the device and system for all types of adult and pediatric cardiac surgery, including, coronary artery bypass surgery, valvular surgery, and other vascular valve surgery requiring cardioplegia.
It is a further advantage of the device and system of the present invention to minimize the delivery of excess solution whereby less water, or other non-blood fluids, is absorbed by the tissues and lungs, reducing post-operative heart strain, thereby shortening the recovery period.
It is a further advantage of the device and system of the present invention to instantaneously select a desired ratio of blood to solution without changing the tubing of certain diameters to tubing different diameter.
The foregoing and more specific objects advantages and features of the present invention will become readily apparent to those skilled in the art from the following detailed description of the preferred embodiment thereof taken in conjunction with the drawings.